Visualization tool for parallel dependency graph evaluation

ABSTRACT

Systems and processes providing a tool for visualizing parallel dependency graph evaluation in computer animation are provided. Runtime evaluation data of a parallel dependency graph may be collected, including the start time and stop time for each node in the graph. The visualization tool may process the data to generate performance visualizations as well as other analysis features. Performance visualizations may illustrate the level of concurrency over time during parallel dependency graph evaluation. Performance visualizations may be generated by graphing node blocks according to node start time and stop time as well as the level of concurrency at a given time to illustrate parallelism. Performance visualizations may enable character technical directors, character riggers, programmers, and other users to evaluate how well parallelism is expressed in parallel dependency graphs in computer animation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/797,895, filed Mar. 12, 2013, which claims priority to U.S.Provisional Application No. 61/679,665 filed with the U.S. Patent andTrademark Office on Aug. 3, 2012, the entire contents of which arehereby incorporated by reference.

BACKGROUND 1. Field

This application relates generally to visualization tools for computerprocesses and, more specifically, to computer systems and processes forvisualizing the state of parallel dependency graph evaluation incomputer animation.

2. Related Art

Visualization tools are available for displaying a graphicalrepresentation of the performance of a computer program. For example,traditional visualization tools may provide a heat map that aidsprogrammers, among others, to identify the most expensive, lengthyprocesses or functions that account for longer program runtimes anddecreased user satisfaction. A programmer may then focus on optimizingthe most expensive, lengthy processes or functions so as to have thegreatest impact on decreasing runtime and improving user satisfaction.

However, while traditional visualization tools may be helpful for serialprocesses, they are less helpful and may even be misleading formultithreaded programs with processes running in parallel. To takeadvantage of multi-core processors capable of processing two, four,eight, twelve, sixteen, or more threads in parallel, programmers, amongothers, are designing programs with multiple threads that can runsimultaneously, thereby decreasing runtime and improving overallperformance. Traditional visualization tools may identify lengthyprocesses running on each of the multiple cores, but optimizing thoseprocesses may, in fact, have little or no impact on a program's overallruntime, thereby misleading programmers and wasting time.

For example, a lengthy process may run concurrently with a chain ofserially dependent processes that run for a longer period of time thanthe concurrently running lengthy process. Traditional visualizationtools may suggest that optimizing the lengthy process will decreaseoverall runtime when, in fact, it will have no effect on the overallruntime since the serially dependent processes running concurrently,despite each being shorter in duration, together are of a longerduration. In such a case, optimization efforts should be directed at theserially dependent processes, but current visualization tools may notlead to that conclusion.

Optimization concerns are especially pertinent in the area of computeranimation, where hundreds of thousands of animation frames may beprocessed to create the complex and detailed scenes in today's animatedfilms. Character technical directors, character riggers, and the likemay develop a dependency graph to render, animate, or otherwise describea scene in an animation. A dependency graph may be made up ofinterconnected nodes, each of which may be a standalone computation unitthat takes in data via one or more input attributes, performs somecomputation on the data, and produces one or more output attributes. Theconnections in the graph may represent data flowing from one node to thenext, with each node performing some computation on the data it receivesto generate its output. A node may have multiple inputs and multipleoutputs, as well as other attributes.

Many nodes may be computed simultaneously on multiple processor cores,but computing chains of nodes, each depending on the last, may requiresignificant processing time. Optimization efforts should, therefore, bedirected at those chains of nodes that directly impact the time it takesto evaluate a dependency graph. However, traditional visualization toolsmay lead character technical directors, character riggers, and the liketo focus on optimizing non-critical nodes rather than the key nodes thatdirectly impact the time it takes for the dependency graph to evaluate.

Thus, an improved visualization tool for parallel dependency graphs (aswell as other multithreaded computer processes) is desired.

SUMMARY

Systems and processes for generating a performance visualization of aparallel dependency graph are described. A data file may be receivedthat includes runtime evaluation entries for nodes in a paralleldependency graph. Runtime evaluation entries may include nodeidentification and runtime duration. The concurrency level for each nodein the parallel dependency graph may be determined based on the numberof concurrently executing nodes in the data file. A node block may begenerated for each of the nodes in the parallel dependency graph. Thesize and the position of each of the node blocks may be determined basedon the concurrency level and runtime duration of each correspondingnode. A performance visualization may be generated with some or all ofthe node blocks with sizes and at positions as determined from theconcurrency level and runtime duration of the corresponding nodes.

A request may be received for characteristics of a particular node blockin the performance visualization. In response to receiving the requestfor characteristics, the corresponding node identification, start time,and stop time may be provided for the particular node block. Theupstream derivation and downstream progeny may also be identified andprovided for the particular node block. A display property of nodeblocks may also be changed based on the upstream derivation anddownstream progeny. A critical path of nodes through the paralleldependency graph may also be determined based on a chain of nodes in theparallel dependency graph with the longest runtime duration. Theposition of node blocks in the performance visualization may bedetermined based on the critical path of nodes through the paralleldependency graph. A display property of node blocks may also be changedbased on the critical path of nodes.

BRIEF DESCRIPTION OF THE FIGURES

The present application can be best understood by reference to thefollowing description taken in conjunction with the accompanying drawingfigures, in which like parts may be referred to by like numerals.

FIG. 1 illustrates an exemplary computer-generated animation scene.

FIG. 2 illustrates an exemplary visualization tool that may be used tooptimize parallel dependency graph evaluation in computer animation.

FIG. 3 illustrates an exemplary parallel dependency graph withinterconnected nodes.

FIG. 4 illustrates an exemplary computer-generated animation scene.

FIG. 5 illustrates an exemplary performance visualization of a paralleldependency graph evaluation.

FIG. 6 illustrates an exemplary performance visualization generated fromevaluating a parallel dependency graph animating a scene of a film.

FIG. 7A illustrates an exemplary process for generating a performancevisualization of a parallel dependency graph evaluation.

FIG. 7B illustrates an exemplary process for generating a performancevisualization that emphasizes the critical path of nodes in a paralleldependency graph.

FIG. 8 illustrates an exemplary computing system.

DETAILED DESCRIPTION

The following description is presented to enable a person of ordinaryskill in the art to make and use the various embodiments. Descriptionsof specific devices, techniques, and applications are provided only asexamples. Various modifications to the examples described herein will bereadily apparent to those of ordinary skill in the art, and the generalprinciples defined herein may be applied to other examples andapplications without departing from the spirit and scope of the variousembodiments. Thus, the various embodiments are not intended to belimited to the examples described herein and shown, but are to beaccorded the scope consistent with the claims.

Various embodiments are described below relating to a visualization toolfor generating a performance visualization of parallel dependency graphsin computer animation. As part of the computer animation process,character technical directors, character riggers, and the like maydevelop a dependency graph, which may be used to render, animate, orotherwise describe a scene in an animated film. A dependency graph mayconsist of interconnected nodes, each of which is a standalonecomputation unit that takes in data via one or more input attributes,performs some computation on the data, and produces one or more outputattributes. Many dependency graph nodes may be computed simultaneouslyon multiple processor cores.

An exemplary visualization tool may include a computer program thatgenerates performance visualizations, statistics, and the like fromruntime analysis data of a parallel dependency graph. The data mayinclude identifying information for the nodes in the parallel dependencygraph, along with the runtime execution start time and stop time of eachnode. The exemplary visualization tool may analyze the data and generatea performance visualization that graphically illustrates the level ofconcurrency during parallel dependency graph evaluation (e.g., how wellparallelism is expressed in a parallel dependency graph or how well aparallel dependency graph utilizes multiple processing cores). The toolmay also generate statistics and a variety of different graphicalillustrations for analyzing parallel dependency graphs.

A software programmer, program designer, technical director, or the likemay then use the performance visualization, statistics, and otherillustrations to visualize data flow and analyze the performance of aparallel dependency graph, in particular how well the paralleldependency graph is structured for parallel execution. Optimizations canthen be directed to those nodes that directly impact overall runtime asillustrated in the performance visualization. Additionally, the orderingor structure of a parallel dependency graph may be modified to expressmore parallelism and reduce overall runtime by focusing on areas in theperformance visualization with extra parallel capacity. Similarly, newnodes may be inserted into areas of a parallel dependency graph wherethe performance visualization illustrates free parallel capacity duringevaluation.

Thousands of nodes may be required to describe and animate a singleframe of a film, so optimizing performance by expressing parallelism maybe vital for an efficient computer animation experience. A performancevisualization tool that illustrates concurrency may thus be particularlyhelpful to character technical directors, character riggers, and thelike to improve performance of parallel dependency graphs, therebyreducing runtime delays in the computer animation process. Given theparticular impact such a tool may have in computer animation, thevarious embodiments herein are described using the example of a paralleldependency graph in the computer animation field. However, the variousembodiments may be used to analyze virtually any type of multithreadedcomputer program or process, and the embodiments should accordingly berecognized as having applicability beyond computer animation.

FIG. 1 illustrates an exemplary computer-generated animation scene.Notably, the scene includes a significant amount of detail that maycorrespond to a significant amount of computation time in rendering thescene (e.g., detailed facial expressions, fur, whiskers, lion's mane,etc.). FIG. 2 illustrates exemplary visualization tool 201 that may beused to optimize the computer animation processes used to generate ascene like that of FIG. 1. Parallel dependency graph 203 may be made upof multiple nodes that perform computations on scene data inputs toproduce output attributes that (at least partially) generate animatedscene 205. An exemplary parallel dependency graph is described infurther detail below with reference to FIG. 3. Evaluation data may becollected from parallel dependency graph 203 and used as an input tovisualization tool 201. For example, the start time and stop time ofeach node in parallel dependency graph 203 may be collected and receivedas an input to visualization tool 201. Visualization tool 201 mayanalyze the evaluation data and generate performance visualization 207to, among other things, illustrate how well parallelism is expressed inparallel dependency graph 203. Exemplary performance visualizations aredescribed in further detail below with reference to FIG. 5 and FIG. 6.Likewise, exemplary processes for generating a performance visualizationof a parallel dependency graph evaluation are described in furtherdetail below with reference to FIG. 7A and FIG. 7B.

Performance visualization 207 may be used by technical directors,character riggers, software programmers, and the like to modify andoptimize parallel dependency graph 203. For example, performancevisualization 207 may include an area where parallelism is visiblylacking, indicating a potential for improving evaluation time by betterexpressing parallelism in that area. Similarly, performancevisualization 207 may show that a particular node in underlying paralleldependency graph 203 is directly contributing to a longer evaluationtime, indicating a potential for improving evaluation time by modifyingthe identified node. Technical directors, character riggers, and thelike may then modify parallel dependency graph 203 based on theinformation displayed in performance visualization 207 to optimizeparallel dependency graph 203 and reduce the evaluation time ingenerating animated scene 205.

FIG. 3 illustrates exemplary parallel dependency graph 300 that maygenerate a computer-generated animation scene like that of FIG. 4.Parallel dependency graph 300 is made up of multiple nodes connected byflowing data. Inputs 302 and 304 may be, for example, data describingthe movement of an animated character (e.g., the lion of FIG. 4), thebackground of a scene (e.g., curtains, carpet, etc. of FIG. 4), a changein time, or any of a variety of characteristics upon which nodes 306 and320 are to perform computations to produce output attributes. Forexample, node 306 may be a motion node or deformer node that animatesthe movement of the lion's arm in FIG. 4. Input 302 may be a time,angle, direction, vector, curve, non-uniform rational basis spline, orany of a variety of other input attributes that node 306 may receive toprocess, for example, the movement of the lion's arm in FIG. 4 from oneposition to another.

As illustrated in FIG. 3, the output produced by node 306 is received asan input to both nodes 308 and 316, indicating that each requires theoutput of node 306 to perform its computation. For example, nodes 308and 316 may correspond to the arm fur and paw of the lion in FIG. 4 andmay use the output of node 306 to produce the detailed fur and pawposition shown in FIG. 4. Similarly, the output of node 308 is receivedas an input to both nodes 310 and 314, while the output of node 316 isreceived as an input to node 318. Node 314 produces output 332, whilethe output of node 310 is received as an input to node 312, whichproduces output 330. Node 318, as illustrated, produces output 334. Thevarious nodes and outputs along the chain beginning with node 306 maythus render the various attributes of the lion shown in FIG. 4.

Similarly, the output of node 320 is received as an input to node 322,the output of which is received as an input to node 324. Node 320 maycorrespond to the motion or deformation of the partially-visible sealshown in FIG. 4 (along with its decorative neck piece). The output ofnode 324 is then received as an input to both nodes 326 and 328, whichproduce outputs 336 and 338, respectively. The various nodes and outputsalong the chain beginning with node 320 may thus render the variousattributes of the partially-visible seal shown in FIG. 4. In otherexamples, outputs 330, 332, 334, 336, and 338 may be any of a variety ofdata used for rendering, animating, or otherwise modifying an animatedcharacter or scene. Although inputs and outputs are illustrated assingle lines in graph 300, inputs and outputs may consist of multipleelements. Importantly, as illustrated, many nodes depend on the outputof another upstream node in order to perform its computation. Forexample, node 322 may wait until node 320 produces its output beforeperforming its computations and producing its output. In practice, whenan attribute or input of a node is changed, its outputs may be marked“dirty,” meaning that any cached values are stale and need to berecomputed. Destinations of the dirty values are likewise marked asdirty, such that a new input to the dependency graph causes a dirtystate to propagate through all affected connections and nodes, requiringreprocessing of the affected dirty nodes in turn to obtain updatedoutputs.

Exemplary parallel dependency graph 300 illustrates the potential forconcurrent processing as many nodes may be computed simultaneously. Forexample, node 306 and node 320 may each be computed concurrently, asthey have separate inputs and are otherwise unconnected. In the exampleof FIG. 4, movements of the lion character corresponding to node 306 maybe computed simultaneously with movements of the seal charactercorresponding to node 320. Similarly, nodes 312, 314, 318, 326, and 328may all be computed simultaneously because they do not depend on theoutputs of each other before performing computations. In contrast,however, graph 300 also illustrates how nodes may depend on other nodes,and chains of nodes may grow large and require significant computingtime. For example, before node 312 may perform its computation, each ofnodes 306, 308, and 310 must first complete their computations in turn.In the example of FIG. 4, the lion's fur likely may not be generateduntil the positions of the lion's limbs are determined by upstreamnodes. These upstream nodes upon which node 312 is dependent may bereferred to as its derivation or provenance. Downstream nodes may bereferred to as a node's progeny (e.g., the downstream dependent progenyof node 308 includes nodes 310, 312, and 314). As parallel dependencygraphs grow to hundreds or thousands of individual nodes (as is typicalin computer animation), the complexity is compounded, and it becomesincreasingly difficult to track and understand how the nodes areinterconnected, and particularly difficult to identify sources of delay.

FIG. 5 illustrates exemplary performance visualization 500 that may begenerated from a runtime evaluation analysis of a multithreaded process,such as an evaluation of parallel dependency graph 300. In theillustrated example, performance visualization 500 may graphicallyillustrate the level of concurrency over time during evaluation ofparallel dependency graph 300. Performance visualization 500 may be inthe form of a graph, as illustrated in FIG. 5, but many other variantsare contemplated for illustrating the level of concurrency duringevaluation of a parallel dependency graph. In one embodiment, thevertical axis may be representative of the level of concurrency, and thehorizontal axis may be representative of time, which may be absolute,relative, approximate, or another variant. Performance visualization 500shows that at time zero (or the absolute time computation began for theparallel dependency graph) two nodes began simultaneously, asrepresented by node blocks 506 and 520. Although the axes may becustomized for a particular organization or application, here,performance visualization 500 is configured to depict that if only onenode is being computed, there is a concurrency level of zero, while eachadditional node running concurrently increments the concurrency level toone, two, and so on.

Performance visualization 500 represents node and node computation timewith blocks that are sized and positioned to illustrate concurrency overtime. Each node block may be positioned horizontally such that theleading edge of the node block corresponds to the time the nodecomputation began, which in some embodiments may be the time when allrequired node inputs became available, the time when the correspondingprocess was scheduled by the operating system to run, or a similar time.The horizontal size of each node block may correspond to its runtimeduration, such that the trailing edge of each node block corresponds tothe stop time of the node computation, the time the node's computedoutputs became available, the time processing passed to the next node,or a similar time. Although node blocks are illustrated as rectangular,stacked blocks, in other embodiments, they may be a different shape, andthe layout of the visualization may be modified (e.g., the axes may beswitched).

Dashed lines 530 and 532 are included as a reference demonstrating howdependencies may be readily identified from performance visualization500. As shown, the leading edges of node blocks 508 and 516 immediatelyfollow the trailing edge of node block 506. In one embodiment, thisproximity may be understood as a potential dependency relationship. Forexample, node blocks 506, 508, and 516 could correspond to nodes 306,308, and 316, respectively, illustrated in FIG. 3. As shown in FIG. 3,nodes 308 and 316 are dependent on node 306; thus dashed line 530 inFIG. 5 emphasizes how correlated stop and start times may indicate adependent relationship between node blocks. Similarly, dashed line 532illustrates a potential dependent relationship between node blocks 524,526, and 528. In one example, these node blocks may correspond to nodes324, 326, and 328, respectively, of FIG. 3, which affirms that nodes 326and 328 are dependent on node 324 and thus require the output of node324 before they can perform their own computation. Other dependenciesare also illustrated, such as node block 510 to node block 512, nodeblock 516 to node block 518, and node blocks 520, 522, and 524 in serialsuccession. In other instances, however, nodes may depend from more thanone other node, and other methods may also be implemented to communicatethe dependency relationship, such as highlighting or coloring nodeblocks to show relationships, listing the dependency relationships,graphing lines showing dependencies, or other techniques.

Character technical directors, riggers, and the like may thus readilyidentify from the layout of performance visualization 500 many potentialdependency relationships among nodes along with node runtime duration,and may use these illustrated dependencies and runtimes in determiningwhich target nodes or portions of the graph may be optimized to improveoverall runtime performance. For example, programmers or other users mayfocus in on portions of performance visualization 500 and may visuallyidentify time expensive node blocks and time expensive node bock chainsand step up through the chain of node blocks—following thedependencies—to identify nodes that should be optimized or areas thatmay be reconfigured to improve processing time. Thus, one embodiment ofa performance visualization with sizing and horizontally positioningnode blocks based on start times and runtime duration (or stop time) maybeneficially provide a quick visual cue of node runtimes and relevantnode dependencies in the underlying parallel dependency graph.

Performance visualization 500, as mentioned above, also illustrates oneembodiment of vertically positioning node blocks to graphicallyillustrate the level of concurrency, or how well parallelism isexpressed in the underlying parallel dependency graph. In oneembodiment, node blocks may be positioned horizontally, as describedabove, to correspond to the start and duration of processing time. Todetermine the vertical position in the graph, node blocks may beassigned to the lowest concurrency level available without overlap. Forexample, process 700 or process 720—described in greater detail belowwith reference to FIG. 7A and FIG. 7B—may be used to generate aperformance visualization and lay out node blocks. In generatingperformance visualization 500, the visualization tool may have firstplaced node block 520 at concurrency level zero. When attempting toinsert node block 506 into the graph, however, node block 520 wouldoverlap node block 506, so the visualization tool may have incrementedthe concurrency level for node block 506 and positioned it asillustrated in performance visualization 500. In another embodiment, thevisualization tool may identify overlapping times—or equivalentlyconcurrently running nodes—from the runtime evaluation data it receives(e.g., a data file that includes runtime evaluation entries). Forexample, the visualization tool may compare start and stop times of theidentified nodes in the runtime evaluation data file to determine whereoverlap occurs. When overlap is identified, the visualization tool mayassign each node in the data file a particular concurrency level suchthat the corresponding node block may be positioned vertically withoutoverlap.

FIG. 5 and performance visualization 500 also illustrate how concurrencymay vary over time, and how the position of subsequent node blocks mayaccordingly change with time as well. For example, at runtime of theunderlying parallel dependency graph from which performancevisualization 500 may have been generated, computation may have begunsimultaneously for both of the nodes corresponding to node blocks 506and 520. After the node corresponding to node block 506 completed,however, two new nodes began computation as illustrated by node blocks508 and 516, for a total of three concurrently executing nodes.Similarly, completion of the node computation corresponding to nodeblock 508 yielded two new computing nodes corresponding to node blocks510 and 514, for a total of four concurrently executing nodes. Thus,with the addition of new nodes independent of other executing nodes, theconcurrency level and vertical position may be incremented to both avoidoverlap and graphically illustrate concurrency in the underlyingparallel dependency graph.

In one embodiment, node blocks may not be decremented in verticalposition mid-stream, which may yield unfilled white space in theperformance visualization, such as that following node block 514. Asillustrated, the completion of the node corresponding to node block 524(marked by dashed line 532) yielded two additional node blocks 526 and528. At that time, the node corresponding to node block 514 was stillcomputing, thus node block 528, to avoid overlap, was positioned atconcurrency level four. After the node corresponding to node block 514finished computing, however, an unfilled white space at concurrencylevel two resulted. In performance visualization 500, node block 528 wasnot lowered part-way through its runtime duration, but instead remainedat concurrency level four. In other embodiments, however, some users mayprefer that all white space be filled to maintain an instantaneouslyaccurate concurrency level. In those embodiments, node block 528 may besplit at the termination of node block 514, and the remainder of nodeblock 528 may be positioned immediately following node block 514,thereby reflecting that the concurrency level at that time haddecremented back to three (or four concurrently executing nodes). One ofordinary skill in the art will recognize that many variations arepossible, and performance visualization tools and performancevisualizations may be customized to fit the needs or preferences ofparticular organizations and particular users.

Users analyzing a parallel dependency graph may be particularlyinterested in the critical path through the parallel dependency graph.The critical path may be the path or chain of nodes that takes thelongest to finish computing, or in other words, the longestpath—measured by runtime duration—through the parallel dependency graph.As computing the critical path by definition may take longer than anyother path in the parallel dependency graph, the critical path may alsocorrespond to the overall computation or evaluation time of the entireparallel dependency graph. In animation, for example, the time tocompute the critical path of nodes may signify the amount of time forthe parallel dependency graph to finish animating, rendering, orotherwise processing an animation scene or character in a scene. Thecritical path of nodes may thus directly correspond to theresponsiveness or efficiency of an animation program, such that longercritical paths, with longer computation times, may yield frustratingdelays. Given the direct impact of the critical path on animationefficiency or animation program responsiveness, character technicaldirectors, riggers, and other users may accordingly prefer to focus onthe critical path for optimization (and arguably should focus effortsthere given the impact). To aid users in this directed optimization,performance visualizations may be configured to emphasize the criticalpath (e.g., change a display property of the node blocks correspondingto nodes on the critical path).

Performance visualization 500 in FIG. 5 illustrates one method ofemphasizing the critical path by positioning critical path node blocksat the lowest vertical position. As illustrated, the node correspondingto node block 526 was the last to finish computing. That indicates thatnode block 526 is on the critical path, as well as some or all of thederivation or provenance nodes that preceded node block 526. In thisexample, ascending the path leading to node block 526 shows that nodeblocks 524, 522, and 520 are also on the critical path (e.g., as shownin FIG. 3, node 326 depends from nodes 324, 322, and 320). In otherwords, the shortest amount of time for evaluating the paralleldependency graph underlying performance visualization 500 is dictated bythe computation time of the nodes corresponding to node blocks 520, 522,524, and 526 (e.g., computing nodes 320, 322, 324, and 326). In thisexample, the critical path of nodes is emphasized by placing these nodeblocks at concurrency level zero, making it easy to walk through thecritical path node blocks to identify areas for optimization. In otherexamples, other display properties of node blocks may be changed; forexample, node blocks corresponding to critical path nodes may be shadedor colored differently than other nodes, connecting lines may be drawnto identify the path, node blocks may include text detailing thecritical path, or any of a variety of other illustration methods may beused to highlight the node blocks corresponding to critical path nodes.

A performance visualization tool may determine which nodes are on thecritical path in a variety of ways, including starting at the last nodeto finish and ascending the derivation nodes through the start time, ateach juncture selecting the next derivation node with a stop timecorresponding to the start time of the current node in the path. Inother examples, a performance visualization tool may walk each paththrough the parallel dependency graph, summing the runtime duration ofeach path to identify the longest path as the critical path of nodes.Walking paths through the parallel dependency graph may be done from theruntime evaluation data file, for example, by summing runtime durationfor each distinct path of nodes, with each distinct path determined fromstart times, stop times, branches out to multiple nodes, andcombinations into fewer nodes. For example, where the outputs of twonodes join to a common progeny node, the derivation node that finishedcomputing last would be included in the running sum for a potentialcritical path including that node, as the path including that derivationnode would be longer. In contrast, where a node's output branches to twoprogeny nodes, two separate paths must be tracked and summed, as eitherpath could be the longest. Many other methods for determining thecritical path of nodes are contemplated, any of which could be used toidentify which node blocks to highlight in the performancevisualization.

In the example shown in FIG. 5, a user reviewing performancevisualization 500 may note that optimizing any of the nodescorresponding to node blocks 520, 522, 524, and 526 may improve overallruntime of the corresponding dependency graph. It should be noted,however, that typical analysis programs may suggest that optimizing thenode corresponding to node block 516 would be preferable because theruntime duration of that node is significantly longer than any othernode. However, optimizing the node corresponding to node block 516 maynot reduce the overall runtime, as the critical path nodes may remainunchanged by those optimizations. Thus, performance visualizations asdiscussed herein may beneficially direct users to more meaningfuloptimizations that are more likely to improve overall runtimeperformance than optimizations suggested by typical analysis programs.

FIG. 6 illustrates exemplary performance visualization 600 generatedfrom evaluating a parallel dependency graph animating a scene of a film.Performance visualization 600 illustrates many variations possible ingenerating a performance visualization of a parallel dependency graph,depending on user needs and preferences. Performance visualization 600includes thousands of distinct node blocks, many of which are finevertical lines that may be distinguished by zooming in on those portionsof the graph. Performance visualization 600 includes a maximumconcurrency level of twelve, with an underlying parallel dependencygraph that may have been running on a twelve-core processor. Of note, atsome points in the graph, thirteen distinct node blocks are in processconcurrently. Of course, at most twelve computations may be processedsimultaneously on a twelve-core processor; however, more than twelvethreads may be in process concurrently, and the operating system mayschedule different threads on an alternating basis on any processorcore. In other words, a node may be in process while occasionally beingsubject to pauses or delays while other processes occupy a processorcore. These pauses or delays may be expected with numerous concurrentthreads as an operating system itself may occupy processor cores toperform scheduling tasks and other operating system tasks. In manyinstances, programmers prefer to allow the operating system scheduler todetermine the optimal distribution of threads across multiple processorcores, and occasional pauses and thread overlap are acceptedconsequences that are visible in performance visualization 600.

Performance visualization 600 also illustrates one embodiment of aperformance visualization with varied shading and coloring that mayindicate a number of different features. In one embodiment, node blockscorresponding to a type of computation may be similarly shaded orcolored, such as shading all deformer-related node blocks the same. Inanother embodiment, node blocks may be shaded or colored to correspondto a particular element in a scene of animation. For example, in a scenewith multiple characters, the node blocks corresponding to animatingeach of the characters may be shaded or colored to identify which nodeblocks correspond to which character. Background animation elements mayalso be shaded or colored differently from other elements. In theanimated scene examples of FIG. 1 and FIG. 4, node blocks may be coloreddifferently for each individual character: the lion, the giraffe, thezebra, and the seal. Similarly, node blocks corresponding to thebackground of these scenes may likewise be colored differently (e.g.,curtains, carpet, walls, etc.).

In another embodiment, node blocks corresponding to different parts of acharacter may be shaded or colored differently, such as different colorsfor face animation node blocks, arm animation node blocks, core or stemanimation node blocks, hair animation node blocks, leg animation nodeblocks, hand and finger animation node blocks, and the like. In theanimated scene examples of FIG. 1 and FIG. 4, for example, the nodeblocks corresponding to the face of the lion may be shaded or coloreddifferently than the node blocks corresponding to the arms of the lion.Similarly, the node blocks corresponding to the paw of the lion may beshaded or colored differently than the node blocks corresponding to thefur and mane of the lion. Both the elements to be distinguished and theshading or coloring methods implemented may be customized based on theneeds and preferences of users. In some embodiments, the performancevisualization may be modified in real time from a user selectingdifferent preferences for display. For example, a user may initiallydisplay the performance visualization with colors distinguishing nodecomputation type, change it later to distinguish based on character, andchange it yet again to distinguish based on parts of characters, asdesired. In the computer animation examples of FIG. 1 and FIG. 4, forexample, a user may initially display different characters withdifferent colors (e.g., lion, zebra, giraffe, seal, etc.) and laterswitch to displaying different core and body parts with different colors(e.g., stem, arms, legs, paws, head, etc.). In some embodiments, a graphkey may be overlaid on the display, imbedded in the graph, provided as apop-up option, or otherwise made available to associate particularcolors or shades with particular elements (e.g., a table associatingcolors with character names, shading with node computation types, etc.).

Performance visualization 600 also illustrates how computer resourceconstraints or parallel dependency graph structures could lead to emptywhite space along concurrency level zero, or, in other embodiments, howonly particular node blocks corresponding to certain nodes on thecritical path may be highlighted or emphasized. As illustrated, thereare several regions of empty white space along concurrency level zero.In one embodiment, such gaps may relate to machine resourcerestrictions. For example, in a computer with twelve processor cores, athirteenth process may be forced to wait until twelve already-runningprocesses complete and the thirteenth process is scheduled and begins torun on a processor. One node in a parallel dependency graph may havethirteen or more downstream dependencies. If twelve dependencies arealready occupying the twelve processors, the remainder of thedependencies may be forced to wait. If one of the remaining dependenciesis a critical node on the critical path, a gap may appear alongconcurrency level zero until the critical path node is processed. Thus,gaps may appear at concurrency level zero when critical path nodes arewaiting for available resources. As illustrated in FIG. 6, gaps mayappear frequently where many nodes are being processed and all processorcores are more likely to be occupied, thereby forcing critical pathnodes to wait for machine resources to become available.

In other embodiments, only serial critical path node blocks may bepositioned at the lowest level of the graph as opposed to all nodes onthe critical path. In particular, the first node block that appears atconcurrency level zero may have depended directly on different inputsfrom multiple nodes previously running in parallel; in other words,before the corresponding node could begin computation, several otherindependent, parallel nodes had to finish computing and provide theiroutput attributes. Similarly, the nodes of some node blocks illustratedin performance visualization 600 at concurrency level zero may havebranched out to multiple nodes, leading to a white space following thenode block where parallelism is expressed; in other words, thecorresponding node's output attributes were an input to multiple othernodes in parallel.

In some instances, users may be less interested in critical path regionsthat already express parallelism (which may include white spaces inperformance visualization 600 along concurrency level zero), and insteadprefer to focus on serial nodes on the critical path. Such serial nodesmay exist where a node depends directly on only one prior node, or wherea node's outputs feed directly into only one other node. Thus, asillustrated in performance visualization 600, the critical path nodeblocks emphasized and positioned at the lowest vertical level mayinclude only those node blocks corresponding to serial nodes on thecritical path, where parallelism is not expressed in computing thecritical path attributes. The node blocks there illustrated may thuscorrespond to key nodes that each individually may have a direct impacton the overall runtime. As such, optimization efforts may be more likelyto have a meaningful impact on overall runtime if directed to reducingthe runtime of the serial nodes on the critical path or modifying theunderlying parallel dependency graph to express parallelism along thoseserial sections in computing critical path output attributes.

In some embodiments, the critical path may be emphasized (i.e., displayproperties of the critical path node blocks may be changed) inperformance visualizations by positioning the corresponding node blocksat the lowest level in the graph as described above. In otherembodiments, the corresponding node blocks may instead be duplicated anddepicted, for example, both at the lowest level in the graph and in linewith nearby provenance or progeny node blocks at other concurrencylevels. In still other embodiments, other display properties may bechanged for critical path node blocks; for example, critical path nodeblocks may be highlighted or otherwise emphasized in the graph in adifferent color, different shape, with different text, or the like.

Although performance visualizations 500 and 600 are illustrated asstatic graphs, performance visualizations may be interactive displays,or may be accessed through a visualization tool providing for userinteraction with the visualization. Many interactions may be exercisedwith a mouse, keyboard, touchscreen, gestures, or the like. In oneembodiment, users may zoom in on any portion of the graph, betterenabling them to see distinct node blocks in high detail, or zoom out,giving a larger perspective overview. Users may also drag the graph viewaround the display screen to focus on specific portions ofvisualizations, scroll the graph view or window in any direction, orstretch the graph view horizontally or vertically as desired. In someembodiments, the mouse pointer or other position indicator mechanism maybe illustrated as a set of crosshairs—intersecting lines that extend tothe axes or across the entire display to allow users to compare startand stop times, concurrency levels, and the like. The position of thecross point of the crosshairs (time and/or concurrency level) may bereported textually on the screen in a text box, a header, a footer, agraph key, or other display.

In some embodiments, a user may request information about a particularnode block by simply directing a mouse pointer or other positionindicator to the node block (e.g., mouse over a node block, positioncrosshairs on a node block, etc.). A visualization tool may then providea variety of information about the particular node block, such as nodename or identification, start time, stop time, runtime duration,derivation nodes, progeny nodes, node type, animation character name,animation character part, and the like. Information may be displayed ina pop-up text box or in a fixed text box overlaid on a portion of thedisplay. In other examples, information may appear in the header orfooter of the display window or the graph. In still other examples,users may request information by a particular keystroke or buttons onthe screen.

Features for changing the display properties (e.g., highlighting oremphasizing) derivation and progeny nodes may also be incorporated intoperformance visualizations. For example, identifying or selecting aparticular node block may cause some or all of the correspondingderivation node blocks and progeny node blocks to be highlighted, shadedor colored differently, otherwise set apart from other node blocks,depicted alone in the visualization, or the like. Keystrokes or othercommands may also be provided to request that a visualization toolmodify the graph to change the display properties of a particular set ofnode blocks (such as related upstream derivation or downstream progenynode blocks).

FIG. 7A illustrates exemplary process 700 for generating a performancevisualization of a parallel dependency graph evaluation. Process 700 maybe executed on a workstation computer, a laptop computer, a tabletcomputer, a mobile handheld computer, a server, across multipleworkstations, across multiple servers, over the internet, or on avariety of other computational devices. Although process 700 may beperformed by a variety of devices and/or programs, for illustrativepurposes, process 700 will be described as being performed by avisualization tool that may be a computer programmed to perform theparticular functions.

At block 702, a visualization tool may receive a data file of a runtimeevaluation of a parallel dependency graph. In one embodiment, the datafile may have been generated by a monitoring tool that records thecomputer clock start time and stop time of each node during evaluationof a parallel dependency graph. For example, the data file may include atable of runtime evaluation entries listing each node in the paralleldependency graph, the time each node started computing, and the timeeach node stopped computing. Each node may be identified in any of avariety of ways, such as a unique identification number, a node name, anode computation type, an affected animation element, or the like. Starttimes may be the computer clock time when a node was scheduled to run,when node inputs became available, when a node began computing, or thelike. Stop times may be the computer clock time when a node wasterminated, when node outputs became available, when a node stoppedcomputing, or the like.

The runtime evaluation data file may also include processor coreidentification for each node (i.e., for each runtime evaluation entry).For example, for a twelve-core processor, the data file may indicatewhich processor or processors (one through twelve) performed thecomputations of each node. In some cases, nodes may themselves bemultithreaded processes that include parallelism, so multiple processorsmay be used to perform node computations in parallel, and any or all ofthose processors may be identified in the data file. In other cases, anoperating system may migrate node computation from one processor toanother processor, and both processors may be identified in the datafile (as well as any additional processors that perform nodecomputations, if any).

The information included in the data file may also be customized basedon the needs and preferences of particular organizations and users. Forexample, in some examples the data file may include a listing of theupstream derivation and downstream progeny of each node (i.e., for eachruntime evaluation entry), a tag identifying the type of computation, apointer or link to other files with parallel dependency graphinformation, a time stamp of when the evaluation was done, networkstatus during evaluation, memory access delay information, the user orusers running the evaluation, or any of a variety of other identifyinginformation that may be useful to a character technical director,rigger, or the like for analyzing and/or improving performance.

At block 704, the visualization tool may determine the level ofconcurrency of executing nodes. In one embodiment, the visualizationtool may scan through the runtime evaluation data file (through eachruntime evaluation entry), incrementing a concurrency count at the starttime of each node, and decrementing the concurrency count at the stoptime of each node. The tool may track how the concurrency level changes,and it may assign a concurrency level to each node in the data file asit traverses across time. In one embodiment, the tool may work backwardsfrom the last node to finish computing up through the first node tobegin, incrementing a concurrency level with each stop time, anddecrementing the level with each start time. In still other embodiments,the tool may traverse the data file and assign concurrency levels toavoid overlap in the ultimate performance visualization, as mentionedabove. Determining the level of concurrency of executing nodes may alsobe done in other ways depending on user preference or a particularimplementation.

At block 706, the performance visualization tool may generate nodeblocks for each node in the parallel dependency graph. In oneembodiment, the tool may populate a graph with each node block and itsassociated information, such as horizontal position, vertical position,size, color, shape, text, identifying information, and the like. In someembodiments, generating node blocks may include causing the node blocksto be stored in a memory representation of the graph, or causing thenode blocks to be drawn or displayed on a graph. In other embodiments,generating node blocks may include creating new node block objects, eachwith characteristics describing how it should be sized and positioned,along with other identifying information, such as node name oridentification and the like. In still other embodiments, generating nodeblocks may include adding new characteristics to a visualization graphobject describing how the graph should be rendered, or otherwiseorganizing node block data in preparation for displaying a graphvisualization. Other embodiments may include other steps for organizingnode block information and preparing it for display.

At block 708, the performance visualization tool may determine the sizeand position of each node block based on the concurrency leveldetermined at block 704 and the runtime duration of each correspondingnode. As illustrated in FIG. 6, each node block may have a widthcorresponding to the runtime duration of the corresponding node.Likewise, the position of each node block may be based at least in parton the concurrency level of each node determined at block 704. Theleading edge of each node block may correspond to its start time, andthe trailing edge to its stop time. The vertical position may be basedon the concurrency level to ensure that node blocks do not overlap,which also may illustrate how well parallelism is expressed in theunderlying parallel dependency graph.

At block 710, the performance visualization tool may generate aperformance visualization (such as those shown in FIG. 5 and FIG. 6)including each of the node blocks with the size and at the positiondetermined at block 708. In one embodiment, generating a performancevisualization may include generating a displayable graph in memory thatincludes each of the node blocks in position. In other embodiments,generating a performance visualization may include causing theperformance visualization to be displayed on a display device, includingone or more of the node blocks as needed to populate a particular viewof the graph. In still other embodiments, generating a performancevisualization may include storing data in memory, in conjunction withother graph information, in preparation for displaying thevisualization.

FIG. 7B illustrates exemplary process 720 for generating a performancevisualization that emphasizes the critical path of nodes in a paralleldependency graph. Process 720 may include some of the same steps asprocess 700, and the two processes may likewise be combined or alteredaccording to user needs.

At block 722, a visualization tool may receive a data file of a runtimeevaluation of a parallel dependency graph just as at block 702 ofprocess 700. At block 724, the visualization tool may generate a newperformance visualization shell (e.g., an object, a graph, a file, aplaceholder, etc.). In some embodiments, generating a new performancevisualization shell may include creating a new performance visualizationfile for storing (temporarily or permanently) the performancevisualization data. In other embodiments, generating a new performancevisualization shell may include causing a blank graph to be generated inmemory, or in some cases, displayed in anticipation of populating thegraph with node blocks. In still other embodiments, generating a newperformance visualization shell may include causing a performancevisualization object to be generated in memory with certain features,where new node blocks and other graph features may be added to theobject as the information is processed or requested. In someembodiments, this step may be omitted entirely or postponed until thevisualization is to be displayed on a display device. Generating a newperformance visualization shell may also be customized in a variety ofother ways based on a particular implementation on a particular systemfor a particular organization and its needs.

At block 726, the visualization tool may determine the level ofconcurrency of executing nodes just as at block 704 of process 700. Atblock 728, the visualization tool may determine the critical paththrough the parallel dependency graph. In one embodiment, the tool maydetermine the critical path at the same time it traverses the data fileto determine concurrency levels. For example, starting with the lastnode to finish computing, the tool may traverse the data file backwardsin time, identifying the concurrency levels along the way, as well astracking the derivation or provenance of the last node to finishcomputing (some of the derivation nodes also being part of the criticalpath, as discussed above). In other embodiments, the tool may walk eachpath through the parallel dependency graph to determine the path withthe longest runtime duration, in some cases by traversing each path inthe data file marked by corresponding start times and stop times. Instill other embodiments, the tool may analyze runtime durations anddependencies using other methods to determine which nodes are on thecritical path. In some examples, the critical path may include onlyserial critical path nodes where parallelism is not expressed in thedependency graph along the critical path. In other examples, the longestnodes in sections with parallelism may be identified as critical pathnodes, or all nodes touching the critical path may be identified ascritical path nodes.

At block 730, the performance visualization tool may generate nodeblocks for each node in the parallel dependency graph just as at block706 of process 700. In generating node blocks at block 730, the tool maymodify a graph, graph object, software object, shell, or the like thatmay have been generated at block 724. At block 732, the performancevisualization tool may graph the concurrency of node blocks over time,emphasizing the critical path. In one embodiment, graphing theconcurrency of node blocks over time may include generating adisplayable graph in memory that includes each of the node blocks inposition. In other embodiments, graphing the concurrency of node blocksover time may include causing the performance visualization to bedisplayed on a display device, including one or more of the node blocksas needed to populate a particular view of the graph. In still otherembodiments, graphing the concurrency of node blocks over time mayinclude storing data in memory, in conjunction with other graphinformation, in preparation for displaying the visualization.Emphasizing the critical path may include any of the methods describedabove, such as emphasizing critical path node blocks with highlighting,shading, coloring, positioning, or the like.

Depending on the particular implementation, some steps of processes 700or 720 may be omitted, modified, or combined together, and the order maybe altered. In addition, in some embodiments, process 700 or process 720may be followed by causing a visualization to be displayed on a displaydevice, which may allow for user interaction that may require redrawingparts of the visualization, which in turn may require repeating somesteps in process 700 or process 720 based on user requests to modifywhat is being displayed.

Many other variants may also be implemented in a visualization tool andin generating performance visualizations. In one embodiment, forexample, node blocks may be marked differently to indicate whether ornot the corresponding node is multithreaded. For example, node blocks ofmultithreaded nodes may be marked with a line, symbol, color, shade,text, or the like to distinguish them from node blocks of singlethreaded nodes. Whether a node is multithreaded may be hard-coded aspart of the runtime evaluation data file or parallel dependency graph,or it may be inferred from runtime evaluation data. In some embodiments,the level of multithreading in a node may be graphically represented bylevels of shading, colors, text, or the like to illustrate how well anode is internally threaded compared to other multithreaded nodes.

In some embodiments, different graphs or visualizations may also begenerated, such as a graph of node blocks organized by processor coreidentification (such as one through twelve) over time. For example, thevertical axis, instead of concurrency level, may be organized byprocessor core identification, and node blocks may be verticallypositioned based on the core identification (or core id) correspondingto the processor core on which the node was computed. In some cases,multithreaded nodes may be distributed across multiple processor cores,so the graph may also illustrate how some nodes themselves exhibitparallelism by stretching a block vertically across multiple processorlevels, or duplicating a similar node block on multiple processor corelevels. In other instances, a single node thread may be moved from onecore to another, so the graph may illustrate thread migrations that inmany cases may add delay as cache values need to be copied, for example.In some embodiments, a visualization tool may include buttons, menuitems, key strokes, or similar commands for causing a processor coreid-type graph to be displayed. In contrast to graphs illustratingconcurrency levels, a processor core id-type graph may be limitedvertically to the number of processor cores, so the graph may alsoillustrate gaps as some nodes are paused and later resumed after anotherprocess is inserted and occupies processing time (e.g., other nodeprocesses, operating system tasks, etc.).

In another embodiment, any of the performance visualizations or graphsdiscussed herein may be modified by filtering the display to show onlycertain node blocks. For example, a performance visualization tool mayinclude a button, check box, menu, toggle, keystroke command, or othercommand method for selecting which node blocks to display. Users may,for example, filter the display to show only those node blockscorresponding to a particular function, node type, character, color,processor core, character element, motion, scene, or the like. In theexample computer animations of FIG. 1 and FIG. 4, for example, users maydisplay only those node blocks corresponding to the lion. Users may alsofilter the display to show only those node blocks on the critical path,or node blocks that are related to critical path nodes (such asderivation nodes or progeny nodes, whether or not they are on thecritical path). Similarly, users may filter the display to show onlythose node blocks relating to a selected node, such as all derivationnode blocks and progeny node blocks of a selected node. As mentionedabove, the display may also be modified to change the display properties(e.g., highlight or emphasize) any of these node blocks in any of theways discussed herein.

Performance visualizations or graphs may also be configured to displaythe dirty state of the corresponding nodes. In some embodiments, nodesin a parallel dependency graph that are dirty may be marked with aparticular level of dirtiness as well, such as heavy dirty, partialdirty, light dirty, or the like. The level of dirtiness may correspondto how significant the reevaluation of a node may be, depending, forexample, on how significantly its input attributes have changed. Forexample, if all input attributes are changed, and a full reevaluation ofa node is required, that node may be considered heavy dirty. Incontrast, if only one of many input attributes has changed, andreevaluation is relatively minor, that node may be considered partialdirty or light dirty. Performance visualizations or graphs may beconfigured to illustrate the level of dirtiness of nodes before theywere recomputed by marking or flagging node blocks in a particular way.For instance, dirty levels may be indicated on node blocks usingshading, colors, symbols, lines, text, or the like. A visualization toolmay also be configured with a check box, button, menu option, toggleoption, keystroke command, or the like for selecting whether or not todisplay the dirty state in a graph or performance visualization.

A visualization tool may also incorporate additional tools for aidingcharacter technical directors, riggers, and other users to analyzeparallel dependency graph performance and even simulate how changes mayaffect performance. In one embodiment, users may be able to drag anddrop node blocks in performance visualizations to see how rearrangingthe underlying parallel dependency graph might affect evaluationperformance. For example, users may identify a lengthy section of serialnode blocks and drag and drop other node blocks in parallel with theserial node blocks (i.e., relocating later node blocks in thevisualization to appear in parallel with the serial section). Similarly,users may insert new node blocks into the visualization taken from othervisualizations or by creating customized blocks to simulate how theperformance visualization might look if the underlying paralleldependency graph were modified to achieve the simulated visualizationwith the new nodes inserted. Although dragging and dropping a node blockis theoretical and may not always be plausible given node dependencies,the ability to simulate the changes may be very useful, and users may beable to more easily visualize how significant an impact such changes mayhave if the parallel dependency graph may be reconfigured in aparticular way. Additionally, inserting new node blocks into an existingvisualization illustrates how available processing time may be utilizedto process nodes that may not yet be a part of a particular paralleldependency graph. Thus, enabling users to modify performancevisualizations and simulate potential changes may provide an additionalaid to users for analyzing parallel dependency graphs and determiningwhere to direct optimization efforts.

A visualization tool may also be configured to report statistics ordiagnostic data. In one embodiment, a visualization tool may provide anaverage graph concurrency, which may be computed as the average numberof nodes running in parallel. By reporting a standard number such asaverage concurrency, different parallel dependency graphs may becompared against each other, and different character technicaldirectors, riggers, or other users may be compared against each other oreven compete against each other for the highest average concurrency asmeasured by this statistic. The statistic may be displayed by userrequest or in response to any of the command methods discussed herein.In some embodiments, average graph concurrency may be computed for anentire parallel dependency graph regardless of what is displayed, but inother embodiments, average graph concurrency may be computed for theportion of a performance visualization that is displayed in avisualization tool window, allowing for finer detail of segments of aparallel dependency graph.

Other analysis tools may also be incorporated into a visualization tool,including enabling a user to load more than one runtime evaluation datafile at time, and display multiple performance visualizations or graphsat a time. In one embodiment, when a user modifies a parallel dependencygraph, they may load a data file collected before the modification alongwith a data file collected after the modification to compare the twovisualizations and see how the modifications affected performance.Similarly, a graph may be generated illustrating the ratio of changefrom one evaluation to another (e.g., one to one, four to one, etc.).Multiple graphs or visualizations may be arranged in a variety of waysto facilitate comparison, such as side by side or vertically aligned. Insome embodiments, unrelated data sets may be loaded simultaneously, andusers may be able to view and interact with multiple visualizations andgraphs simultaneously. For example, a project manager may load multipledata files generated from each of the parallel dependency graphs relatedto the project to allow quick comparisons of the various graphs and thestatistics of each graph. Users may also be able to coordinateinteractions with multiple displayed graphs or visualizations, such asduplicating crosshairs on each graph at the same position, coordinatinggraph modifications such as zooming such that it occurs on multiplegraphs simultaneously, or the like. In other embodiments, multipleinstances of a visualization tool may be able to run on the samemachine, independent of one another.

Other visualization or graph views may also be incorporated into avisualization tool to provide additional analysis aids. In oneembodiment, a category view may be provided. A category view mayillustrate graphically the summed category runtime for all nodes relatedto each category like face, wardrobe, hair, and the like. Node blocks orother figures may be graphed to compare the amount of time spent on eachcategory, such as a bar graph with each category listed on one axis andsummed time on the other axis. Similar category views may also beprovided for other category types such as frames, node functions,characters, scene elements, or the like, to allow a visual comparison ofthe different total runtimes of the different elements in each category.In one embodiment, selecting a particular bar or otherwise identifying aparticular element in the graph (by double-clicking, for example) maycause a performance visualization to be displayed that includes nodeblocks corresponding to the particular element selected.

In another embodiment, a concurrency histogram view may be provided. Thehistogram may graphically illustrate how much time a certain number ofcores are being used or how much time a certain number of nodes areconcurrently executing. For example, a visualization tool may sum thetime one node is executing, the time two nodes are concurrentlyexecuting, the time three nodes are concurrently executing, and so on.The summed time may then be displayed in a histogram format with barssized to illustrate the length of time a particular number of nodes orcores were processing. In this way, where parallelism is betterexpressed, histogram bars corresponding to larger numbers ofconcurrently executing nodes should be much larger than histogram barscorresponding to smaller numbers of concurrently executing nodes. Such aconcurrency histogram view may thus provide another reference foranalyzing how well parallelism is expressed in a parallel dependencygraph.

A visualization tool may also provide methods of identifying the mostexpensive nodes in a parallel dependency graph. In one embodiment, avisualization tool may provide a list of all nodes and theircorresponding runtimes, and the list may be sorted by runtime such thatthe nodes with the longest runtimes are listed first (or last, asdesired). In another embodiment, a visualization tool may provide agraph view of all nodes and their corresponding runtimes. Such a graphmay have an axis corresponding to runtime, with another axis listingeach node, optionally sorted by runtime such that the nodes with thelongest runtimes appear at the opposite extreme from the nodes with theshortest runtimes. Such a graph may include lines, dots, symbols, or thelike sized and/or positioned to illustrate runtimes. In one embodiment,a user may mouse over or otherwise select a particular node in theruntime comparison list or graph, which may cause display properties tobe changed for the corresponding node block in a performancevisualization (e.g., highlighted or otherwise emphasized) to enable theuser to quickly see where the node block appears.

It should be noted that the various embodiments described herein withreference to parallel dependency graphs in animation may also be used inthe context of any other multithreaded computer programs and processes.An exemplary visualization tool in such a context may include a computerprogram that generates performance visualizations, statistics, and thelike from runtime analysis data of a multithreaded computer program orprocess. The data may include identifying information for the variousthreads, processes, or sub-processes in the computer program, along withthe runtime execution start time and stop time of each thread, process,or sub-process. The exemplary visualization tool may analyze the dataand generate a performance visualization that graphically illustratesthe level of concurrency during program execution (e.g., how wellparallelism is expressed in a program or how well a program utilizesmultiple processing cores). The tool may also generate statistics and avariety of different graphical illustrations for analyzing multithreadedprograms just as for parallel dependency graphs as discussed herein.

A software programmer, program designer, technical director, or the likemay then use the performance visualization, statistics, and otherillustrations to visualize data flow and analyze the performance of aprogram, in particular how well the program is structured for parallelexecution. Optimizations can then be directed to those threads,processes, or sub-processes that directly impact overall runtime asillustrated in the performance visualization. Additionally, the orderingor structure of a program or process may be modified to express moreparallelism and reduce overall runtime by focusing on areas in theperformance visualization with extra parallel capacity. Similarly, newprocesses or additional threads may be inserted into areas of amultithreaded program where the performance visualization illustratesfree parallel capacity during evaluation. Thus, the various embodimentsand examples discussed herein for parallel dependency graphs may bereadily extended to any other multithreaded computer program or process.

FIG. 8 illustrates an exemplary computing system 800 configured toperform any one of the above-described processes. In this context,computing system 800 may include, for example, a processor (which mayhave multiple cores), memory, storage, and input/output devices (e.g.,monitor, keyboard, disk drive, Internet connection, etc.). However,computing system 800 may include circuitry or other specialized hardwarefor carrying out some or all aspects of the processes. In someoperational settings, computing system 800 may be configured as a systemthat includes one or more units, each of which is configured to carryout some aspects of the processes either in software, hardware, or somecombination thereof.

FIG. 8 depicts an exemplary computing system 800 with a number ofcomponents that may be used to perform the above-described processes.The main system 802 includes a motherboard 804 having an input/output(“I/O”) section 806, one or more central processing units (“CPU”) 808(which may have multiple cores), and a memory section 810, which mayhave a flash memory card 812 related to it. The I/O section 806 isconnected to a display 824, a keyboard 814, a disk storage unit 816, anda media drive unit 818. The media drive unit 818 can read/write anon-transitory computer-readable storage medium 820, which can containprograms 822 or data.

At least some values based on the results of the above-describedprocesses can be saved for subsequent use. Additionally, anon-transitory computer-readable storage medium can be used to store(e.g., tangibly embody) one or more computer programs for performing anyone of the above-described processes by means of a computer. Thecomputer program may be written, for example, in a general purposeprogramming language (e.g., Pascal, C, C++) or some specializedapplication-specific language.

Although only certain exemplary embodiments have been described indetail above, those skilled in the art will readily appreciate that manymodifications are possible in the exemplary embodiments withoutmaterially departing from the novel teachings and advantages of thisdisclosure. For example, aspects of embodiments disclosed above can becombined in other combinations to form additional embodiments.Accordingly, all such modifications are intended to be included withinthe scope of this disclosure.

What is claimed is:
 1. A computer implemented method for generating aperformance visualization of a parallel dependency graph in computeranimation, the method comprising: obtaining an execution time of a firstnode of the parallel dependency graph; determining a concurrency levelfor the first node of the parallel dependency graph based on a number ofother nodes executing concurrently with the first node of the paralleldependency graph and concurrency levels for at least a portion of theother nodes executing concurrently with the first node; determining alength of a first node block corresponding to the first node, whereinthe length of the first node block represents runtime duration of thefirst node block; determining, based on the concurrency level of thefirst node, a position along a first axis for the first node block,wherein positions along the first axis represent concurrency levels ofrespective nodes; determining, based on the obtained execution time ofthe first node, a position along a second axis for the first node block,wherein positions along the second axis represent execution times ofrespective nodes; and generating a performance visualization of theparallel dependency graph with the first node block: placed along thefirst axis in accordance with the position representing the concurrencylevel of the first node, placed along the second axis in accordance withthe position representing the execution time of the first node, andsized along the second axis such that an entirety of the length of thefirst node block is in accordance with the position representing theconcurrency level of the first node, visually indicating that theconcurrency level of the first node is constant throughout the runtimeduration of the first node block.
 2. The computer-implemented method ofclaim 1 further comprising: determining a critical path of nodes throughthe parallel dependency graph; when the first node is part of thecritical path, placing the first node block in a predetermined levelalong the first axis.
 3. The computer-implemented method of claim 1further comprising: obtaining an execution time of a second node of theparallel dependency graph, wherein the first and second nodes aredifferent nodes; determining a concurrency level for the second node ofthe parallel dependency graph based on a number of nodes, including thefirst node, executing concurrently with the second node of the paralleldependency graph; determining a length of a second node blockcorresponding to the second node, wherein the length of the second nodeblock represents runtime duration of the second node block; determining,based on the concurrency level of the second node, a position along asecond axis for the second node block; determining, based on theobtained execution time of the second node, a position along a secondaxis for the second node block, wherein the position along the secondaxis for the second node block is within a range along the second axisof the first node block; and wherein generating the performancevisualization of the parallel dependency graph includes the second nodeblock: placed along the first axis in accordance with the positionrepresenting the concurrency level of the second node, placed along thesecond axis in accordance with the position representing the executiontime of the second node, and sized along the second axis in accordancewith the length representing runtime duration of the second node.
 4. Thecomputer-implemented method of claim 3 further comprising: when placingthe second node block along the first axis and when the execution timeof the first and second nodes overlap, placing the second node block ata concurrency level above the first node block.
 5. Thecomputer-implemented method of claim 3 further comprising: when leadingedges of the first and second node blocks are proximate a trailing edgeof a third node block, visually depicting a dependency relationshipamongst the first, second, and third node blocks.
 6. Thecomputer-implemented method of claim 3 further comprising: determiningan overhang of the first node comprising: if a fourth node starts beforea stop time of a third node and before the start times of the first andthe second nodes; and the fourth node terminates after a stop time ofthe third node, after the start times of the first and second nodes, andbefore stop times of the first and second nodes; and in accordance withthe determining the overhang of the first node, splitting the first nodeblock.
 7. The computer-implemented method of claim 6, wherein splittingthe first node block comprises: splitting the first node block into afirst portion and a second portion, wherein the first portion has alength that represents runtime duration from the start of the first nodeand termination of the fourth node, and wherein the second portion has alength that represents runtime duration from the termination of thefourth node to a stop time of the first node; and positioning the secondportion of the first node block immediately following the fourth nodeblock.
 8. The computer-implemented method of claim 3 further comprising:receiving a request for characteristics of the first node block; and inresponse to receiving the request for characteristics of the first nodeblock, providing the corresponding node identification, start time, andstop time of the first node block.
 9. The computer-implemented method ofclaim 8 further comprising: in response to receiving the request forcharacteristics of the first node block: when the second node is anupstream derivation of the first node associated with the correspondingfirst node block, providing information about the second node as anupstream derivation of the first node block; and when the second node isa downstream progeny of the first node associated with the correspondingfirst node block, providing information about the second node as adownstream progeny of the first node block.
 10. The computer-implementedmethod of claim 9 further comprising: displaying the performancevisualization of the parallel dependency graph; and in response toreceiving the request for characteristics of the first node block,changing a display property of the second node block based on the secondnode block being an upstream derivation or a downstream progeny of thefirst node block.
 11. A non-transitory computer-readable storage mediumstoring one or more programs configured to be executed by one or moreprocessors for generating a performance visualization of a paralleldependency graph in computer animation, the one or more programscomprising instructions for: obtaining an execution time of a first nodeof the parallel dependency graph; determining a concurrency level forthe first node of the parallel dependency graph based on a number ofother nodes executing concurrently with the first node of the paralleldependency graph and concurrency levels for at least a portion of theother nodes executing concurrently with the first node; determining alength of a first node block corresponding to the first node, whereinthe length of the first node block represents a runtime duration of thefirst node block; determining, based on the concurrency level of thefirst node, a position along a first axis for the first node block,wherein positions along the first axis represent concurrency levels ofrespective nodes; determining, based on the obtained execution time ofthe first node, a position along a second axis for the first node block,wherein positions along the second axis represent execution times ofrespective nodes; and generating a performance visualization of theparallel dependency graph with the first node block: placed along thefirst axis in accordance with the position representing the concurrencylevel of the first node, placed along the second axis in accordance withthe position representing the execution time of the first node, andsized along the second axis such that an entirety of the length of thefirst node block is in accordance with the position representing theconcurrency level of the first node, visually indicating that theconcurrency level of the first node is constant throughout the runtimeduration of the first node block.
 12. The non-transitorycomputer-readable storage medium of claim 11, wherein the one or moreprograms further include instructions for: obtaining an execution timeof a second node of the parallel dependency graph, wherein the first andsecond nodes are different nodes; determining a concurrency level forthe second node of the parallel dependency graph based on a number ofnodes executing concurrently with the second node of the paralleldependency graph; determining a length of a second node blockcorresponding to the second node, wherein the length of the second nodeblock represents runtime duration of the second node block; determining,based on the concurrency level of the second node, a position along thefirst axis for the second node block; determining, based on the obtainedexecution time of the second node, a position along the second axis forthe second node block; and wherein generating the performancevisualization of the parallel dependency graph includes the second nodeblock: placed along the first axis in accordance with the positionrepresenting the concurrency level of the second node, placed along thesecond axis in accordance with the position representing the executiontime of the second node, and sized along the second axis in accordancewith the length representing runtime duration of the second node. 13.The non-transitory computer-readable storage medium of claim 12, whereinthe one or more programs further include instructions for: when placingthe second node block along the first axis, determining if the executiontime of the first and second nodes overlap; and in accordance with adetermination that the execution times of the first and second nodesoverlap, placing the second node block at a concurrency level above thefirst node block.
 14. The non-transitory computer-readable storagemedium of claim 13, wherein determining if the execution times of thefirst and second nodes overlap comprises instructions for: comparingstart and stop times of the first and second nodes.
 15. Thenon-transitory computer-readable storage medium of claim 12, wherein: aleading edge of the first node block corresponds to a start time ofexecution of the first node; and a leading edge of the second node blockcorresponds to a start time of execution of the second node.
 16. Thenon-transitory computer-readable storage medium of claim 15, wherein theone or more programs further include instructions for: determining ifthe leading edges of the first and second node blocks are proximate atrailing edge of a third node block; and in accordance with adetermining that the leading edges of the first and second node blocksare proximate the trailing edge of the third node block, visuallydepicting a dependency relationship amongst the first, second, and thirdnode blocks.
 17. The non-transitory computer-readable storage medium ofclaim 15, wherein the one or more programs further include instructionsfor: determining an overhang of the first node comprising: if a fourthnode starts before a stop time of a third node and before the starttimes of the first and the second nodes; and the fourth node terminatesafter a stop time of the third node, after the start times of the firstand second nodes, and before stop times of the first and second nodes;and in accordance with the determining the overhang of the first node,splitting the first node block.
 18. The non-transitory computer-readablestorage medium of claim 17, wherein splitting the first node blockincludes instructions for: splitting the first node block into a firstportion and a second portion, wherein the first portion has a lengththat represents runtime duration from the start of the first node andtermination of the fourth node, and wherein the second portion has alength that represents runtime duration from the termination of thefourth node to a stop time of the first node; and positioning the secondportion of the first node block immediately following the fourth nodeblock.
 19. The non-transitory computer-readable storage medium of claim12, wherein the one or more programs further include instructions for:receiving a request for characteristics of the first node block; and inresponse to receiving the request for characteristics of the first nodeblock, providing the corresponding node identification, start time, andstop time of the first node block.
 20. The non-transitorycomputer-readable storage medium of claim 19, wherein the one or moreprograms further include instructions for: in response to receiving therequest for characteristics of the first node block: in accordance withidentifying the second node as an upstream derivation of the first nodeassociated with the corresponding first node block, providinginformation about the second node as an upstream derivation of the firstnode block; and in accordance with identifying the second node as adownstream progeny of the first node associated with the correspondingfirst node block, providing information about the second node as adownstream progeny of the first node block.
 21. The non-transitorycomputer-readable storage medium of claim 20, wherein the one or moreprograms further include instructions for: causing the performancevisualization of the parallel dependency graph to be displayed; and inresponse to receiving the request for characteristics of the first nodeblock, changing a display property of the second node block based on thesecond node block being an upstream derivation or a downstream progenyof the first node block.
 22. The non-transitory computer-readablestorage medium of claim 11, wherein the one or more programs furtherinclude instructions for: determining a critical path of nodes throughthe parallel dependency graph; determining whether the first node ispart of the critical path; and in accordance with a determination thatthe first node is part of the critical path, placing the first nodeblock in a predetermined level along the first axis.
 23. Thenon-transitory computer-readable storage medium of claim 22, wherein thepredetermined level is the lowest level along the first axis.
 24. Thenon-transitory computer-readable storage medium of claim 22, wherein theone or more programs further include instructions for: assigning adisplay property of the first node block based on the first node blockbeing part of the critical path.
 25. The non-transitorycomputer-readable storage medium of claim 22, wherein determining acritical path of nodes comprises instructions for: determining a lastnode to finish; and from the determined last node, ascending derivationnodes through the parallel dependency graph.
 26. The non-transitorycomputer-readable storage medium of claim 25, wherein ascendingderivation nodes comprises instructions for: at a juncture of the firstnode and a second node, wherein the second node is a current derivationnode, determining if a stop time of the second node corresponds with thestart time of the first node; and in accordance with a determinationthat the stop time of the second node corresponds with the start time ofthe first node, selecting the first node as the current derivation node.27. The non-transitory computer-readable storage medium of claim 22,wherein determining a critical path of nodes comprises instructions for:summing runtime duration of each path through the parallel dependencygraph; and identifying the path with the longest runtime duration as thecritical path.
 28. A computer system for generating a performancevisualization of a parallel dependency graph in computer animation, thesystem comprising: a display; one or more processors; and anon-transitory computer-readable storage medium storing one or moreprograms configured to be executed by the one or more processors, theone or more programs comprising instructions for: determining aconcurrency level for the first node of the parallel dependency graphbased on a number of other nodes executing concurrently with the firstnode of the parallel dependency graph and concurrency levels for atleast a portion of the other nodes executing concurrently with the firstnode; determining a length of a first node block corresponding to thefirst node, wherein the length of the first node block represents aruntime duration of the first node block; determining, based on theconcurrency level of the first node, a position along a first axis forthe first node block, wherein positions along the first axis representconcurrency levels of respective nodes; determining, based on theobtained execution time of the first node, a position along a secondaxis for the first node block, wherein positions along the second axisrepresent execution times of respective nodes; and generating, fordisplay on the display, a performance visualization of the paralleldependency graph with the first node block: placed along the first axisin accordance with the position representing the concurrency level ofthe first node, placed along the second axis in accordance with theposition representing the execution time of the first node, and sizedalong the second axis such that an entirety of the length of the firstnode block is in accordance with the position representing theconcurrency level of the first node, visually indicating that theconcurrency level of the first node is constant throughout the runtimeduration of the first node block.
 29. The system of claim 28, whereinthe one or more programs further include instructions for: obtaining anexecution time of a second node of the parallel dependency graph,wherein the first and second nodes are different nodes; determining aconcurrency level for the second node of the parallel dependency graphbased on a number of nodes, including the first node, executingconcurrently with the second node of the parallel dependency graph;determining a length of a second node block corresponding to the secondnode, wherein the length of the second node block represents a runtimeduration of the second node block; determining, based on the concurrencylevel of the second node, a position along a second axis for the secondnode block; determining, based on the obtained execution time of thesecond node, a position along a second axis for the second node block,wherein the position along the second axis for the second node block iswithin a range along the second axis of the first node block; andwherein generating the performance visualization of the paralleldependency graph includes the second node block: placed along the firstaxis in accordance with the position representing the concurrency levelof the second node, placed along the second axis in accordance with theposition representing the execution time of the second node, and sizedalong the second axis in accordance with the length representing runtimeduration of the second node.